Mobile wireless communications devices are by definition transportable, and because of this it is sometimes complicated to ensure continued connectivity to such devices. For example, many carriers and providers exist, and a user may venture into areas where their chosen provider does not have equipment available to provide the desired service. In these instances, the user is said to be “roaming.” Roaming entails the use of a network other than the user's assigned or chosen primary carrier and network.
When a device is in a roaming condition, the user will be charged by the operator of the new network, and may be charged a different, and potentially much larger, fee than they typically pay to their primary network. In addition, since they generally are still required to pay their primary network, this situation can result in the incurrence of exorbitant fees in a short amount of time. To ameliorate this situation, network providers typically have certain partners that they prefer to use for roaming services. The use of the partner facilities enable the mobile user to incur lower charges, and in some cases receive better service, than they otherwise would have.
With respect to CDMA, PCS and other services for example, the selected partner networks are typically listed in what has come to be known as a Preferred Roaming List (PRL). The PRL is a data file that lists alternative networks for use when a primary wireless network is not reachable. The PRL typically lists bands, sub bands and service provider identifiers that a device should accept. A mobile wireless, e.g., cellular, device may or may not be able to obtain service outside of a home area without the PRL, and in addition, if the device is able to roam, the incurred fees may be significant without a PRL. Fundamentally, the PRL typically allows the mobile device to select a best carrier when roaming. For example, roaming partners may provide discounted roaming rate agreements, so it is desirable to use such carriers when possible, while avoiding carriers that may not be affiliated with the primary network and which may therefore charge a premium roaming fee to users.
Thus, it is generally advisable for the PRL for a mobile device be maintained in a reasonably up-to-date state. This is especially important for users that travel and use their device outside of their home area frequently. Not only are such mobile users more likely to use other networks, but they are more likely to make substantial use of such carriers and thus to incur significant overcharges if lack of an appropriate PRL prevents them from using preferred roaming partners.
However, attempting to access a carrier listed on the PRL may be inefficient for several reasons. For example, a carrier may not be available on the same side of the wireless band as the home side. Even if a carrier is available on the same side as the home side, the carrier may be of a technology that is not compatible with the mobile device. Another reason for inefficiency is that the accessible carrier may not have a roaming agreement with the mobile device's home carrier. Further, it is sometimes the case that the only accessible carrier may be on the opposite side of the cellular band or in the PCS band. A better system is needed for selecting appropriate networks and carriers when a device is outside of its home area.